source: src/ResolvExpr/ResolveAssertions.cc@ 1d60da8

ADT arm-eh ast-experimental enum forall-pointer-decay jacob/cs343-translation jenkins-sandbox new-ast new-ast-unique-expr pthread-emulation qualifiedEnum
Last change on this file since 1d60da8 was b4f8808, checked in by Andrew Beach <ajbeach@…>, 6 years ago

Removed lvalue from types in the old ast.
  • Property mode set to 100644
File size: 18.0 KB
Line 
1//
2// Cforall Version 1.0.0 Copyright (C) 2015 University of Waterloo
3//
4// The contents of this file are covered under the licence agreement in the
5// file "LICENCE" distributed with Cforall.
6//
7// ResolveAssertions.cc --
8//
9// Author : Aaron B. Moss
10// Created On : Fri Oct 05 13:46:00 2018
11// Last Modified By : Andrew Beach
12// Last Modified On : Thu Aug 8 16:47:00 2019
13// Update Count : 3
14//
15
16#include "ResolveAssertions.h"
17
18#include <algorithm> // for sort
19#include <cassert> // for assertf
20#include <list> // for list
21#include <memory> // for unique_ptr
22#include <sstream> // for ostringstream
23#include <string> // for string
24#include <unordered_map> // for unordered_map, unordered_multimap
25#include <utility> // for move
26#include <vector> // for vector
27
28#include "Alternative.h" // for Alternative, AssertionItem, AssertionList
29#include "Common/FilterCombos.h" // for filterCombos
30#include "Common/Indenter.h" // for Indenter
31#include "Common/utility.h" // for sort_mins
32#include "GenPoly/GenPoly.h" // for getFunctionType
33#include "ResolvExpr/RenameVars.h" // for renameTyVars
34#include "SymTab/Indexer.h" // for Indexer
35#include "SymTab/Mangler.h" // for Mangler
36#include "SynTree/Expression.h" // for InferredParams
37#include "TypeEnvironment.h" // for TypeEnvironment, etc.
38#include "typeops.h" // for adjustExprType, specCost
39#include "Unify.h" // for unify
40
41namespace ResolvExpr {
42 /// Unified assertion candidate
43 struct AssnCandidate {
44 SymTab::Indexer::IdData cdata; ///< Satisfying declaration
45 Type* adjType; ///< Satisfying type
46 TypeEnvironment env; ///< Post-unification environment
47 AssertionSet have; ///< Post-unification have-set
48 AssertionSet need; ///< Post-unification need-set
49 OpenVarSet openVars; ///< Post-unification open-var set
50 UniqueId resnSlot; ///< Slot for any recursive assertion IDs
51
52 AssnCandidate( const SymTab::Indexer::IdData& cdata, Type* adjType, TypeEnvironment&& env,
53 AssertionSet&& have, AssertionSet&& need, OpenVarSet&& openVars, UniqueId resnSlot )
54 : cdata(cdata), adjType(adjType), env(std::move(env)), have(std::move(have)),
55 need(std::move(need)), openVars(std::move(openVars)), resnSlot(resnSlot) {}
56 };
57
58 /// List of candidate assertion resolutions
59 using CandidateList = std::vector<AssnCandidate>;
60
61 /// Reference to single deferred item
62 struct DeferRef {
63 const DeclarationWithType* decl;
64 const AssertionSetValue& info;
65 const AssnCandidate& match;
66 };
67
68 /// Wrapper for the deferred items from a single assertion resolution.
69 /// Acts like indexed list of DeferRef
70 struct DeferItem {
71 const DeclarationWithType* decl;
72 const AssertionSetValue& info;
73 CandidateList matches;
74
75 DeferItem( const DeclarationWithType* decl, const AssertionSetValue& info, CandidateList&& matches )
76 : decl(decl), info(info), matches(std::move(matches)) {}
77
78 bool empty() const { return matches.empty(); }
79
80 CandidateList::size_type size() const { return matches.size(); }
81
82 DeferRef operator[] ( unsigned i ) const { return { decl, info, matches[i] }; }
83 };
84
85 /// List of deferred resolution items
86 using DeferList = std::vector<DeferItem>;
87
88 /// Combo iterator that combines candidates into an output list, merging their environments.
89 /// Rejects an appended candidate if the environments cannot be merged.
90 class CandidateEnvMerger {
91 /// Current list of merged candidates
92 std::vector<DeferRef> crnt;
93 /// Stack of environments to support backtracking
94 std::vector<TypeEnvironment> envs;
95 /// Stack of open variables to support backtracking
96 std::vector<OpenVarSet> varSets;
97 /// Indexer to use for merges
98 const SymTab::Indexer& indexer;
99
100 public:
101 /// The merged environment/open variables and the list of candidates
102 struct OutType {
103 TypeEnvironment env;
104 OpenVarSet openVars;
105 std::vector<DeferRef> assns;
106 Cost cost;
107
108 OutType( const TypeEnvironment& env, const OpenVarSet& openVars,
109 const std::vector<DeferRef>& assns )
110 : env(env), openVars(openVars), assns(assns), cost(Cost::infinity) {}
111 };
112
113 CandidateEnvMerger( const TypeEnvironment& env, const OpenVarSet& openVars,
114 const SymTab::Indexer& indexer )
115 : crnt(), envs{ env }, varSets{ openVars }, indexer(indexer) {}
116
117 bool append( DeferRef i ) {
118 TypeEnvironment env = envs.back();
119 OpenVarSet openVars = varSets.back();
120 mergeOpenVars( openVars, i.match.openVars );
121
122 if ( ! env.combine( i.match.env, openVars, indexer ) ) return false;
123
124 crnt.emplace_back( i );
125 envs.emplace_back( env );
126 varSets.emplace_back( openVars );
127 return true;
128 }
129
130 void backtrack() {
131 crnt.pop_back();
132 envs.pop_back();
133 varSets.pop_back();
134 }
135
136 OutType finalize() { return { envs.back(), varSets.back(), crnt }; }
137 };
138
139 /// Comparator for CandidateEnvMerger outputs that sums their costs and caches the stored
140 /// sums
141 struct CandidateCost {
142 using Element = CandidateEnvMerger::OutType;
143 private:
144 const SymTab::Indexer& indexer; ///< Indexer for costing
145
146 public:
147 CandidateCost( const SymTab::Indexer& indexer ) : indexer(indexer) {}
148
149 /// reports the cost of an element
150 Cost get( Element& x ) const {
151 // check cached cost
152 if ( x.cost != Cost::infinity ) return x.cost;
153
154 // generate cost
155 Cost k = Cost::zero;
156 for ( const auto& assn : x.assns ) {
157 // compute conversion cost from satisfying decl to assertion
158 k += computeConversionCost(
159 assn.match.adjType, assn.decl->get_type(), false, indexer, x.env );
160
161 // mark vars+specialization cost on function-type assertions
162 FunctionType* func = GenPoly::getFunctionType( assn.match.cdata.id->get_type() );
163 if ( ! func ) continue;
164
165 for ( DeclarationWithType* formal : func->parameters ) {
166 k.decSpec( specCost( formal->get_type() ) );
167 }
168 k.incVar( func->forall.size() );
169 for ( TypeDecl* td : func->forall ) {
170 k.decSpec( td->assertions.size() );
171 }
172 }
173
174 // cache and return
175 x.cost = k;
176 return k;
177 }
178
179 /// compares elements by cost
180 bool operator() ( Element& a, Element& b ) const {
181 return get( a ) < get( b );
182 }
183 };
184
185 /// Set of assertion resolutions, grouped by resolution ID
186 using InferCache = std::unordered_map< UniqueId, InferredParams >;
187
188 /// Lexicographically-ordered vector of costs
189 using CostVec = std::vector< Cost >;
190
191 int compare( const CostVec & a, const CostVec & b ) {
192 unsigned i = 0;
193 do {
194 // lex-compare where shorter one is less
195 if ( i == a.size() ) {
196 return i == b.size() ? 0 : -1;
197 }
198 if ( i == b.size() /* && i < a.size() */ ) return 1;
199
200 int c = a[i].compare( b[i] );
201 if ( c != 0 ) return c;
202 } while ( ++i );
203 assert(!"unreachable");
204 }
205
206 bool operator< ( const CostVec & a, const CostVec & b ) { return compare( a, b ) < 0; }
207
208 /// Flag for state iteration
209 enum IterateFlag { IterateState };
210
211 /// State needed to resolve a set of assertions
212 struct ResnState {
213 Alternative alt; ///< Alternative assertion is rooted on
214 AssertionList need; ///< Assertions to find
215 AssertionSet newNeed; ///< New assertions for current resolutions
216 DeferList deferred; ///< Deferred matches
217 InferCache inferred; ///< Cache of already-inferred parameters
218 CostVec costs; ///< Costs of recursive assertion satisfaction for disambiguation
219 SymTab::Indexer& indexer; ///< Name lookup (depends on previous assertions)
220
221 /// Initial resolution state for an alternative
222 ResnState( Alternative & a, SymTab::Indexer & indexer )
223 : alt(a), need(), newNeed(), deferred(), inferred(), costs{ Cost::zero }, indexer(indexer) {
224 need.swap( a.need );
225 }
226
227 /// Updated resolution state with new need-list
228 ResnState( ResnState && o, IterateFlag )
229 : alt(std::move(o.alt)), need(o.newNeed.begin(), o.newNeed.end()), newNeed(), deferred(),
230 inferred(std::move(o.inferred)), costs(o.costs), indexer(o.indexer) {
231 costs.emplace_back( Cost::zero );
232 }
233 };
234
235 /// Binds a single assertion, updating resolution state
236 void bindAssertion( const DeclarationWithType * decl, AssertionSetValue info, Alternative & alt,
237 AssnCandidate & match, InferCache & inferred ) {
238
239 const DeclarationWithType * candidate = match.cdata.id;
240 assertf( candidate->uniqueId, "Assertion candidate does not have a unique ID: %s", toString( candidate ).c_str() );
241
242 Expression * varExpr = match.cdata.combine( alt.cvtCost );
243 delete varExpr->result;
244 varExpr->result = match.adjType->clone();
245 if ( match.resnSlot ) { varExpr->resnSlots.push_back( match.resnSlot ); }
246
247 // place newly-inferred assertion in proper place in cache
248 inferred[ info.resnSlot ][ decl->get_uniqueId() ] = ParamEntry{
249 candidate->uniqueId, candidate->clone(), match.adjType->clone(), decl->get_type()->clone(),
250 varExpr };
251 }
252
253 /// Adds a captured assertion to the symbol table
254 void addToIndexer( AssertionSet & assertSet, SymTab::Indexer & indexer ) {
255 for ( auto& i : assertSet ) {
256 if ( i.second.isUsed ) {
257 indexer.addId( i.first );
258 }
259 }
260 }
261
262 // in AlternativeFinder.cc; unique ID for assertion resolutions
263 extern UniqueId globalResnSlot;
264
265 /// Resolve a single assertion, in context
266 bool resolveAssertion( AssertionItem & assn, ResnState & resn ) {
267 // skip unused assertions
268 if ( ! assn.info.isUsed ) return true;
269
270 // lookup candidates for this assertion
271 std::list< SymTab::Indexer::IdData > candidates;
272 resn.indexer.lookupId( assn.decl->name, candidates );
273
274 // find the candidates that unify with the desired type
275 CandidateList matches;
276 for ( const auto & cdata : candidates ) {
277 const DeclarationWithType * candidate = cdata.id;
278
279 // build independent unification context for candidate
280 AssertionSet have, newNeed;
281 TypeEnvironment newEnv{ resn.alt.env };
282 OpenVarSet newOpenVars{ resn.alt.openVars };
283 Type * adjType = candidate->get_type()->clone();
284 adjustExprType( adjType, newEnv, resn.indexer );
285 renameTyVars( adjType );
286
287 // keep unifying candidates
288 if ( unify( assn.decl->get_type(), adjType, newEnv, newNeed, have, newOpenVars,
289 resn.indexer ) ) {
290 // set up binding slot for recursive assertions
291 UniqueId crntResnSlot = 0;
292 if ( ! newNeed.empty() ) {
293 crntResnSlot = ++globalResnSlot;
294 for ( auto& a : newNeed ) {
295 a.second.resnSlot = crntResnSlot;
296 }
297 }
298
299 matches.emplace_back( cdata, adjType, std::move(newEnv), std::move(have),
300 std::move(newNeed), std::move(newOpenVars), crntResnSlot );
301 } else {
302 delete adjType;
303 }
304 }
305
306 // break if no suitable assertion
307 if ( matches.empty() ) return false;
308
309 // defer if too many suitable assertions
310 if ( matches.size() > 1 ) {
311 resn.deferred.emplace_back( assn.decl, assn.info, std::move(matches) );
312 return true;
313 }
314
315 // otherwise bind current match in ongoing scope
316 AssnCandidate& match = matches.front();
317 addToIndexer( match.have, resn.indexer );
318 resn.newNeed.insert( match.need.begin(), match.need.end() );
319 resn.alt.env = std::move(match.env);
320 resn.alt.openVars = std::move(match.openVars);
321
322 bindAssertion( assn.decl, assn.info, resn.alt, match, resn.inferred );
323 return true;
324 }
325
326 /// Associates inferred parameters with an expression
327 struct InferMatcher {
328 InferCache& inferred;
329
330 InferMatcher( InferCache& inferred ) : inferred( inferred ) {}
331
332 Expression* postmutate( Expression* expr ) {
333 // defer missing inferred parameters until they are hopefully found later
334 std::vector<UniqueId> missingSlots;
335 // place inferred parameters into resolution slots
336 for ( UniqueId slot : expr->resnSlots ) {
337 // fail if no matching parameters found
338 auto it = inferred.find( slot );
339 if ( it == inferred.end() ) {
340 missingSlots.push_back( slot );
341 continue;
342 }
343 InferredParams& inferParams = it->second;
344
345 // place inferred parameters into proper place in expression
346 for ( auto& entry : inferParams ) {
347 // recurse on inferParams of resolved expressions
348 entry.second.expr = postmutate( entry.second.expr );
349 // xxx - look at entry.second.inferParams?
350 auto res = expr->inferParams.emplace( entry.first, entry.second );
351 assert(res.second);
352 }
353 }
354
355 // clear resolution slots and return
356 expr->resnSlots.swap( missingSlots );
357 return expr;
358 }
359 };
360
361 /// Map of alternative return types to recursive assertion satisfaction costs
362 using PruneMap = std::unordered_map<std::string, CostVec>;
363
364 /// Gets the pruning key for an alternative
365 std::string pruneKey( const Alternative & alt ) {
366 Type* resType = alt.expr->result->clone();
367 alt.env.apply( resType );
368 std::string resKey = SymTab::Mangler::mangleType( resType );
369 delete resType;
370 return resKey;
371 }
372
373 /// Replace resnSlots with inferParams and add alternative to output list, if meets pruning
374 /// threshold.
375 void finalizeAssertions( ResnState& resn, PruneMap & pruneThresholds, AltList& out ) {
376 // prune if cheaper alternative for same key has already been generated
377 std::string resKey = pruneKey( resn.alt );
378 auto it = pruneThresholds.find( resKey );
379 if ( it != pruneThresholds.end() ) {
380 if ( it->second < resn.costs ) return;
381 } else {
382 pruneThresholds.emplace_hint( it, resKey, resn.costs );
383 }
384
385 // replace resolution slots with inferred params, add to output
386 PassVisitor<InferMatcher> matcher{ resn.inferred };
387 resn.alt.expr = resn.alt.expr->acceptMutator( matcher );
388 out.emplace_back( resn.alt );
389 }
390
391 /// Limit to depth of recursion of assertion satisfaction
392 static const int recursionLimit = 4;
393 /// Maximum number of simultaneously-deferred assertions to attempt concurrent satisfaction of
394 static const int deferLimit = 10;
395
396 void resolveAssertions( Alternative& alt, const SymTab::Indexer& indexer, AltList& out, std::list<std::string>& errors ) {
397 // finish early if no assertions to resolve
398 if ( alt.need.empty() ) {
399 out.emplace_back( alt );
400 return;
401 }
402
403 // build list of possible resolutions
404 using ResnList = std::vector<ResnState>;
405 SymTab::Indexer root_indexer{ indexer };
406 ResnList resns{ ResnState{ alt, root_indexer } };
407 ResnList new_resns{};
408
409 // Pruning thresholds by result type of the output alternatives.
410 // Alternatives *should* be generated in sorted order, so no need to retroactively prune
411 PruneMap thresholds;
412
413 // resolve assertions in breadth-first-order up to a limited number of levels deep
414 for ( unsigned level = 0; level < recursionLimit; ++level ) {
415 // scan over all mutually-compatible resolutions
416 for ( auto& resn : resns ) {
417 // stop this branch if already found a better option
418 auto it = thresholds.find( pruneKey( resn.alt ) );
419 if ( it != thresholds.end() && it->second < resn.costs ) goto nextResn;
420
421 // make initial pass at matching assertions
422 for ( auto& assn : resn.need ) {
423 // fail early if any assertion is not resolvable
424 if ( ! resolveAssertion( assn, resn ) ) {
425 Indenter tabs{ 3 };
426 std::ostringstream ss;
427 ss << tabs << "Unsatisfiable alternative:\n";
428 resn.alt.print( ss, ++tabs );
429 ss << (tabs-1) << "Could not satisfy assertion:\n";
430 assn.decl->print( ss, tabs );
431
432 errors.emplace_back( ss.str() );
433 goto nextResn;
434 }
435 }
436
437 if ( resn.deferred.empty() ) {
438 // either add successful match or push back next state
439 if ( resn.newNeed.empty() ) {
440 finalizeAssertions( resn, thresholds, out );
441 } else {
442 new_resns.emplace_back( std::move(resn), IterateState );
443 }
444 } else if ( resn.deferred.size() > deferLimit ) {
445 // too many deferred assertions to attempt mutual compatibility
446 Indenter tabs{ 3 };
447 std::ostringstream ss;
448 ss << tabs << "Unsatisfiable alternative:\n";
449 resn.alt.print( ss, ++tabs );
450 ss << (tabs-1) << "Too many non-unique satisfying assignments for "
451 "assertions:\n";
452 for ( const auto& d : resn.deferred ) {
453 d.decl->print( ss, tabs );
454 }
455
456 errors.emplace_back( ss.str() );
457 goto nextResn;
458 } else {
459 // resolve deferred assertions by mutual compatibility
460 std::vector<CandidateEnvMerger::OutType> compatible = filterCombos(
461 resn.deferred,
462 CandidateEnvMerger{ resn.alt.env, resn.alt.openVars, resn.indexer } );
463 // fail early if no mutually-compatible assertion satisfaction
464 if ( compatible.empty() ) {
465 Indenter tabs{ 3 };
466 std::ostringstream ss;
467 ss << tabs << "Unsatisfiable alternative:\n";
468 resn.alt.print( ss, ++tabs );
469 ss << (tabs-1) << "No mutually-compatible satisfaction for assertions:\n";
470 for ( const auto& d : resn.deferred ) {
471 d.decl->print( ss, tabs );
472 }
473
474 errors.emplace_back( ss.str() );
475 goto nextResn;
476 }
477 // sort by cost for overall pruning
478 CandidateCost coster{ resn.indexer };
479 std::sort( compatible.begin(), compatible.end(), coster );
480
481 for ( auto& compat : compatible ) {
482 ResnState new_resn = resn;
483
484 // add compatible assertions to new resolution state
485 for ( DeferRef r : compat.assns ) {
486 AssnCandidate match = r.match;
487 addToIndexer( match.have, new_resn.indexer );
488 new_resn.newNeed.insert( match.need.begin(), match.need.end() );
489
490 bindAssertion( r.decl, r.info, new_resn.alt, match, new_resn.inferred );
491 }
492
493 // set mutual environment into resolution state
494 new_resn.alt.env = std::move(compat.env);
495 new_resn.alt.openVars = std::move(compat.openVars);
496
497 // mark cost of this path
498 new_resn.costs.back() += compat.cost;
499
500 // either add sucessful match or push back next state
501 if ( new_resn.newNeed.empty() ) {
502 finalizeAssertions( new_resn, thresholds, out );
503 } else {
504 new_resns.emplace_back( std::move(new_resn), IterateState );
505 }
506 }
507 }
508 nextResn:; }
509
510 // finish or reset for next round
511 if ( new_resns.empty() ) return;
512 resns.swap( new_resns );
513 new_resns.clear();
514 }
515
516 // exceeded recursion limit if reaches here
517 if ( out.empty() ) {
518 SemanticError( alt.expr->location, "Too many recursive assertions" );
519 }
520 }
521} // namespace ResolvExpr
522
523// Local Variables: //
524// tab-width: 4 //
525// mode: c++ //
526// compile-command: "make install" //
527// End: //
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